Taking fish oil supplements can improve the attention and calm children with ADHD, an Australian study has found.

Ph.D. researcher Natalie Sinn, from the University of South Australia and CSIRO Nutrition, said children with ADHD who took a commercial supplement of fish oil and primrose oil showed significant improvements in their attention span and vocabulary.

Their behavior also improved: they were not as restless, impulsive or hyperactive as those who did not take the omega 3-rich fish oil.

Sinn said her study of 145 children with ADHD-related problems showed the fish oil supplement appeared to affect the brain's functioning without any apparent adverse effects in children.

"Sixty per cent of the brain is composed of fats, the most important being polyunsaturated omega-3 and omega-6 fatty acids, and these must be obtained through diet, such as dark leafy vegetables, walnuts, linseed and oil," she said. "There is now a growing body of research to suggest that some children with developmental problems, including ADHD and dyslexia, can benefit from taking omega-3 supplements."

Michele Toner, president of the Learning and Attentional Disorders Society of WA, said some studies had investigated the use of fatty acids in children.

Some showed promising improvement in symptoms relating to ADHD but not necessarily in children who had been officially diagnosed.

"If the Adelaide study has done that, then it is a welcome addition to ADHD research," she said. "But it's important to know whether ADHD subtypes were differentiated, and whether co-existing conditions were accounted for in this research.

"The supplement may be more effective in different subtypes and with certain co-existing conditions, so in order for the research to be helpful it needs to inform parents what the optimum dose is, and how long it takes for the supplement to start taking effect."

Toner said people should always tell their doctors if they took any natural remedies, as seemingly benign medicines could cause problems.

Cost was also an issue, as fatty acid supplements could be expensive.